1. Field of the Invention
The present invention relates to a method of manufacturing a conductive adhesive that is appropriate for a flip chip bonding, and more particularly, to a method of manufacturing a conductive adhesive that is appropriate for a high frequency package, and having a low dielectric constant.
2. Description of the Related Art
Electronic packaging is a wide and various system-manufacturing technology including all processing steps from the semiconductor device to the final product. The semiconductor technology that is abruptly developing in these days enables to integrate cells of one million or more. Particularly, non-memory device technology is being advanced toward many number of I/O pins, larger die size, larger heat radiation, high electrical performance, and so on. However, the electronic packaging technology for packaging these devices does not keep pace with the abrupt advancement of the semiconductor industries.
The electronic packaging is a very important technology of deciding performance, size, price, reliability and so on of the final electronic product, and has a tendency in that its stature becomes more important in recent electronic products pursuing high electrical performance, micro miniaturization/high density, low power consumption, multifunction, high speed signal processing, permanent reliability, etc. Especially, micro packaging element is an essential one used in computer, information telecommunications, wireless mobile telecommunications, high price home electronics, or the like. Among the micro packaging technologies, the utilization range of the flip chip bonding technology that is one of the technologies for electrically connecting the chip on the substrate is currently widened in display packaging appliances, such as smart card, liquid crystal display (LCD), plasma display panel, etc., computer, handheld terminal, telecommunications system, etc.
However, since these flip chip bonding technologies are subject to a complicated bonding process including coating of solder flux on to the substrate, alignment of solder bump-formed chip and surface electrode-formed substrate, reflow of solder bump, removal of remaining flux, and filling and hardening of underfill, they are drawbacks in that the process becomes complicated, and the manufactured product is a very expensive.
Thus, in order to decrease the number of the aforementioned steps, there increases an interest on wafer-based packaging technology in which a polymer material having functions of flux and underfill in the wafer state is coated and process.Also, there are many researches on the flip chip bonding technologies using conductive adhesive and having advantages of low price compared with a general solder flip chip, realization of micropitch electrode, friendly environment excluding the use of flux or lead component, carrying out of low temperature process and so on.
The conductive adhesive is largely classified into anisotropic conductive adhesive (xe2x80x98ACAxe2x80x99) and isotropic conductive adhesive each of which basically contains conductive particles, such as nickel (Ni), Au/polymer, silver (Ag) or the like, and a blend type Insulating resin in which thermosetting and thermoplastic properties are mixed. Further, there is being introduced a flip chip technology using non-conductive adhesive (xe2x80x98NCAxe2x80x99) not containing conductive particles.
Researches on the flip chip technologies using environment-friendly anisotropic conductive film or paste as a bonding material have been actively carried out. With these researches, there are being diffused development researches of conductive adhesive material and application researches on the flip chip technologies using the conductive adhesive. Also, there are actively carried out researches on utilization possibility of the conductive adhesive and development of bonding mechanism of the conductive adhesive.
Further, as there recently increase interests on high speed/high density radio frequency packaging using the flip chip technology, there accordingly increase interests on use of the conductive adhesive as the flip chip bonding material of the RF device instead of use of solder. However, such conventional trials have a limitation in wide and various use because they have electromagnetic coupling problem in the RF region of the conventional conductive adhesive flip chip technology and occurrence problem of resonance phenomenon.
Accordingly, the present invention has been devised to solve the foregoing problems of the prior art, and it is an object of the invention to provide a method for manufacturing a conductive adhesive having a low dielectric constant by adding non-conductive particles to the conventional anisotropic conductive adhesive.
It is another object of the invention to provide a method for manufacturing a conductive adhesive capable of improving the radio frequency characteristic by after the flip chip connection of the RF device, decreasing electromagnetic coupling phenomenon occurring between conductive components, and thus decreasing parasitic components in the connection portion of the flip chip assembly.
It is further another object of the invention to provide a method for manufacturing a conductive adhesive capable of decreasing product defects due to agglutination between conductive particles and non-conductive particles distributed in a thermosetting resin.
To accomplish the above object and other advantages, there is a method of manufacturing a conductive adhesive for a high frequency flip chip package application. The method comprises: a first step of preparing a resin compound by mixing 15-25% by weight solid bisphenol A type epoxy resin, 40-50% by weight liquid bisphenol F type epoxy resin, and 30-40% by weight phenoxy resin; a second step of agitating and mixing the resin compound with an organic solvent in which methyl-ethyl ketone and toluene are mixed in a volume ratio of 1:3, to form a thermosetting resin; a third step of mixing the thermosetting resin with conductive particles and non-conductive particles that have been surface-treated in methyl-ethyl ketone or xcex3-glycidoxypropyl-trimethoxysilane; and a fourth step of mixing a resulting composition of the third seep with an imidazole-based hardener in which the imidazole based hardener is mixed with the resulting composition of the third step by 15-30 g per 100 g of epoxy resin contained in the resulting composition for prevention of agglutination. It is noted that since a resin such as acrylate or the like can be used as the polymer resin instead of the aforementioned epoxy, the claims of the present invention is not limited to the epoxy resin alone.
Preferably, the second step is carried out at a temperature range of 85-95xc2x0 C. for 24-36 hours.
Preferably, the conductive particle is comprised of nickel-, copper-, or gold-coated polymer balls.
Preferably, the conductive particles have a size ranged from 4-10 xcexcm.
The conductive particle is comprised of one selected from the group consisting of SiO2, Teflon, and nano-void. Preferably, the conductive particles have a size of less than 1 xcexcm in diameter.
According to another aspect of the invention, the method may further comprise a step of adding xcex3-glycidoxypropyl-trimethodxysilane to the resulting composition of the third step to prevent agglutination of the particles between the third step and the fourth step.
Selectively, the method, after the fourth step, further comprises a fifth step of placing the resulting composition of the fourth step in a vacuum state to remove impurities including voids.
According to further another aspect of the invention, the method further comprises a step of forming a film having a constant thickness on a releasing paper film by applying a doctor blade method, or a comma roll method to the resulting composition of the fifth step after the fifth step.
Preferably, the film shaped adhesive has a thickness ranged from 10 xcexcm to 50 xcexcm.